Silage aid, process for preparing this silage aid and use of this silage aid

ABSTRACT

This invention relates to a new silage aid, process for preparation of this silage aid and use of the silage aid. The silage aid comprises at least one antioxidant selected from the group 2,6-di-tert-butyl-4-methylphenol (BHT), 3-tert-butyl-4-hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), tocopherol and gallates; at least one short chain caboxylic acid; and optionally at least one salt of said acid. These andoxidants are food approve. The present silage aid is useful for preservation of organic by-products, and particularly for protection of fish oil during a fish silage process.

This application is a 371 application of PCT/NO00/00079 filed Mar. 6,2000.

This invention relates to a new silage aid, process for preparation ofthis silage aid and use of the silage aid.

When preparing silage from for instance fish waste, the raw material istreated with acid to obtain the optimum pH (3.5-4.5) with regard toenzymatic hydrolysis, and to prevent the growth of bacteria duringstorage.

During the silage process hydrolysis results in the formation ofemulsions made up of an acidic water phase, an oil phase and solids. Thedegree of phase separation in these systems depends upon the type of rawmaterial used. Oxygen is easily transferred through water, whichunfortunately gives rise to oxidative degradation of the oil phase. Thislipid oxidation results, of course, in a reduced nutritional value ofthe oil as an ingredient both for feed and for food. Likewise, itimplies a reduced quality of the oleochemicals made from fish silageoil. To overcome these problems it would be a great advantage if anantioxidant well suited for the protection of fish oil could be presentduring the silage process.

The most favourable way to include an antioxidant would be as aconstituent of the silage aid. Generally, it would be necessary to haveat least 1% antioxidant in the silage aid. Water soluble antioxidantsare easily included in an acidic silage aid. Unfortunately though, thesecompounds will not be able to protect the oil after separation sincethey will not be associated with the oil phase. Furthermore, theantioxidants that are food approved in Europe and/or the US at present,are mainly fat soluble compounds. e.g.2.6-di-tert-butyl-4-methylphenol(BHT),3-tert-butyl-4-hydroxyanisole(BHA), tert-butylhydroquinone(TBHQ),tocopherol and the gallates. All of these food approved antioxidants arealso commercially available in formulations with emulsifying agents, butunfortunately the emulsifying agents are in general hydrophobic and thusthese formulations are not well suited to an acidic water medium.

The antioxidant ethoxyquin is an exception with regard to the propertiesdescribed above. Ethoxyquin is a secondary cyclic amine. Hence, it iswell known that ethoxyquin is soluble in acids at low pH (<3), as thisimplies protonation of the amino croup and thereby formation of ahydrophilic salt. As pH rises to 4-5 however, ethoxyquin will bedeprotonated and consequently, will again become fat soluble. Thus, bychoosing the proper concentration of acid it is possible to haveethoxyquin in the form of a hydrophilic salt in the silage aid, whileduring the silage process the salt is deprotonated, becomes fat solubleand consequently will be able to protect the oil against lipidoxidation. Likewise, other antioxidants with an amino group may besuitable for this use. The preparation of ethoxyquin formiate salt, andthis salt dissolved in formic acid is disclosed in Norwegian patentapplication no. 851007.

Unfortunately though, ethoxyquin or other known antioxidants with anamino group, are not food approved. Therefore, when food approval hasbeen required, no silage aid soluble antioxidants have been available todate.

Thus it is a main object of the present invention to provide a newsilage aid comprising a food approved antioxidant.

This and other objects of the invention is achieved by the attachedclaims.

The invention will be further explained below.

The antioxidants BHT, BHA, tocopherol, TBHQ and propyl gallate(PG) arepractically insoluble in water, and experiments have shown that theirsolubility in mineral acids (hydrogen chloride, sulphuric acid) is alsoquite low (see Table 1). Unexpectedly however, we have now found thatthese highly hydrophobic antioxidants are soluble in the short chaincaboxylic acids formic, acetic and propionic acid (see Table 1). Furtherexperiments have shown that when using a silage aid comprising BHA, TBHQor PG dissolved in 85% formic acid, a superior quality of the fish oilproduct as compared to the product of the same process using only 85%formic acid (Table 2) is obtained. When the silage aid containingantioxidant is blended with the fish waste raw material, the hydrophobicantioxidant is associated with and protects the oil phase. Thus, we havefound a method which is convenient on a technical scale and which leadsto superior quality of the products of the silage process.

Generally, the amount of silage aid needed will depend upon the type offish waste used and the choice of acid. Also, the amount of antioxidantneeded may depend upon the raw material used or the requirementsregarding the stability of the isolated oil. This implies that therequired amount of antioxidant dissolved in the acid may vary.

Furthermore, we have shown by experiments that the solubility of BHT informic acid increases when BHA is present in the acid. This was asurprising result.

The silage aid might further comprise additives like, anti-microbiellcompounds (e.g. ethyl benzoate or benzoic acid), anti-fungal compounds,anti-corrosive compounds, chelating compounds (e.g. citric acid),compounds improving the handling properties (e.g. glycerol), and oxygenscavengers.

The present invention also comprises to firstly dissolve the saidantioxidants in a short chain carboxylic acid, and subsequently adding amineral acid in the purpose of decreasing pH.

The short chain carboxylic acids according to this invention might beused either alone or in combination with their corresponding salts.Further, the aforementioned acids might be used as a mixture or as amixture together with any of their salts.

The present invention is documented by experiments performed for a fishsilage process. This invention will of course also prevail for otherprocesses where acidic preservation is used. Fish silage shall only beconsidered as an example. The invention is applicable in acidicpreservation of other organic by-products like slaughter waste, poultrywaste and food waste, as well.

TABLE 1 Solubility (weight %) of antioxidants in different acids. Toco-BHA TBHQ PG BHT pherol 5 M <0.1% <0.1% <0.1% <0.1%  <0.1% hydrogenchloride^(a) 4 N <0.1% <0.1% <0.1% <0.1%  <0.1% sulphuric acid^(a) 85% >5% >5% >10% <0.25%  <0.5% formic acid^(b) 98-100% >10% >10% >10%<0.25%^(c) <0.5% formic acid^(b) 100% >10% >10% >10% >10%  >10% aceticacid^(b) 100% >10% >10% <10% >10%  >10% propionic acid^(b) ^(a)A mixtureof antioxidant(40 mg) and mineral acid(40 g) was thoroughly shaken at23° C. ^(b)A mixture of the chosen amount of antioxidant(10-400 mg) andacid(4 g) was thoroughly shaken at 23° C. ^(c)0.25% BHT is not solublein formic acid. When 0.5% BHA is added to the formic acid. BHT issoluble.

EXAMPLE I Experimental Procedure for a Lab-scale Fish Silage Process

The raw material, Atlantic salmon viscera, was ground in a kitchengrinder, and the resulting minced fish waste was thoroughly blendedbefore it was portioned into separate batches each containing 500 gram.Silage aid (2% vol./wt.; 10 mL) 85% formic acid with or without 0.75%wt./vol. of dissolved antioxidant was added, and the content of eachbatch was mixed to ensure a homogenous distribution. The batches wasstored for eight days in an oven at 35±2° C. before a standard procedurefor silage work up was conducted. This included warming the silage at90±1° C. for 1 minute, tempering, and finally separating the oil aftercentrifugation. The isolated oils were analysed to determine the POV andp-AV. Furthermore, weight gain (at 35±1° C.) as a function of time wasregistered to determine the IP of the oils. The results are presented inTable 2.

Example II

Experimental procedure as in Example I, but the raw material in thisseries was whole herring. The results are presented in Table 2.

TABLE 2 Comparison of the results from analysis of various oil qualityparameters^(a), determined for fish silage oil produced^(b) using silageaid with or without dissolved antioxidant. Example no. Silage aid^(c)POV p-AV IP I Control: 85% HCOOH (formic acid)  3 24  1 85% HCOOH incl.BHA  2 22 19 (150 ppm) 85% HCOOH incl. TBHQ  1  9 62 (150 ppm) IIControl: 85% HCOOH 29 29  0 85% HCOOH incl. PG  7 19  4 (150 ppm)^(a)POV(Peroxide value, Ph. Eur. V.3.4.5); determines the amount ofprimary oxidation products, hydroperoxides, in the oil. p-AV(p-Anisidinevalue, IUPAC 2.504); determines the amount of some secondary oxidationproducts, alkenals, in the oil. IP(induction period); a measure of theshelf life of the oil, given as the number of days it takes before theoil shows detectable weight gain due to oxygen absorption. ^(b)Theexperimental procedure for lab-scale silage experiments is given abovein example I. ^(c)The concentration of antioxidant given inparenthesis,is based on the amount of fish waste used in theseexperiments.

What is claimed is:
 1. A silage aid comprising at least one antioxidantselected from the group consisting of 2,6-di-tert-butyl-4-methylphenol(BHT), 3-tert-butyl-4-hydroxyanisole (BHA), tert-butylhydroquinone(TBHQ), tocopherol and gallates, dissolved in at least one short chaincarboxylic acid selected from the group consisting of formic acid,acetic acid and propionic acid; and optionally at least one salt of saidacids.
 2. A silage aid according to claim 1, wherein the short chaincarboxylic acid is formic acid of concentration 60-100%.
 3. A silage aidaccording to claim 2, wherein the concentration of formic acid is83-98%.
 4. A silage aid according to claim 1, wherein the short chaincarboxylic acid is acetic acid or propionic acid of concentration60-100%.
 5. A silage aid according to claim 4, wherein the concentrationof acetic acid or propionic acid is 80-100%.
 6. A silage aid accordingto claim 1, wherein 0.1-10% of the antioxidant is dissolved in the shortchain carboxylic acid.
 7. A silage aid according to claim 6, wherein theconcentration of antioxidant is 0.3-2%.
 8. A silage aid according toclaim 1, comprising an antioxidant selected from the group consisting ofBHA, TBHQ and propyl galate (PG); and formic acid.
 9. A silage aidaccording to claim 1, comprising BHA and BHT; and formic acid.
 10. Aprocess for preparation of a silage aid comprising at least oneantioxidant selected from the group consisting of2,6-di-tert-butyl-4-methylphenol (BHT), 3-tert-butyl-4-hydroxyanisole(BHA), tert-butylhydroquinone (TBHQ), tocopherol and gallates; at leastone short chain carboxylic acid selected from the group consisting offormic acid, acetic acid and propionic acid; and optionally at least onesalt of said acids, which comprises dissolving at least one of theantioxidants in at least one of the acids.
 11. A process according toclaim 10, wherein 0.1-10% of the antioxidant is dissolved in a shortchain carboxylic acid of concentration 60-100%.
 12. A process accordingto claim 11, wherein the concentration of antioxidant is 0.3-2%.
 13. Aprocess according to claim 10, wherein 0.1-10% of the antioxidant isdissolved in formic acid, acetic acid and/or propionic acid ofconcentration 60-100%.
 14. A process according to claim 13, wherein theconcentration of antioxidant is 0.3-2%.
 15. A process according to claim10, for preparation of a silage aid comprising2,6-di-tert-butyl-4-methylphenol (BHT) and 3-tert-butyl-4-hydroxyanisole(BHA), and formic acid, which comprises a) dissolving BHA in the acid,and b) subsequently, dissolving BHT in the solution obtained in step a).16. A method for protection of fish oil during a fish silage process,which comprises incorporating into the silage a silage aid comprising atleast one antioxidant selected from the group consisting of2,6-di-tert-butyl-4-methylphenol (BHT), 3-tert-butyl-4-hydroxyanisole(BHA), tert-butylhydroquinone (TBHQ), tocopherol and gallates, dissolvedin at least one short chain carboxylic acid selected from the groupconsisting of formic acid, acetic acid and propionic acid; andoptionally at least one salt of said acids.
 17. A method of preservationof organic by-products which comprises incorporating into theby-products a silage aid comprising at least one antioxidant selectedfrom the group consisting of 2,6-di-tert-butyl-4-methylphenol (BHT),3-tert-butyl-4-hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ),tocopherol and gallates, dissolved in at least one short chaincarboxylic acid selected from the group consisting of formic acid,acetic acid and propionic acid; and optionally at least one salt of saidacids.
 18. A silage aid according to claim 2, wherein 0.1-10% of theantioxidant is dissolved in the short chain carboxylic acid.
 19. Asilage aid according to claim 18, wherein the concentration ofantioxidant is 0.3-2%.
 20. A silage aid according to claim 4, wherein0.1-10% of the antioxidant is dissolved in the short chain carboxylicacid.
 21. A silage aid according to claim 20, wherein the concentrationof is 0.3-2%.
 22. A silage aid according to claim 2, comprising anantioxidant selected from the group consisting of BHA, TBHQ and propylgalate (PG); and formic acid.
 23. A silage aid according to claim 4,comprising an antioxidant selected from the group consisting of BHA,TBHQ and propyl galate (PG); and formic acid.
 24. A silage aid accordingto claim 6, comprising an antioxidant selected from the group consistingof BHA, TBHQ and propyl galate (PG); and formic acid.
 25. A silage aidaccording to claim 2, comprising BHA and BHT; and formic acid.
 26. Asilage aid according to claim 4, comprising BHA and BHT; and formicacid.
 27. A silage aid according to claim 6, comprising BHA and BHT; andformic acid.
 28. A silage aid according to claim 8, comprising BHA andBHT; and formic acid.
 29. A process according to claim 11, wherein0.1-10% of the antioxidant is formic acid, acetic acid and/or propionicacid of concentration 60-100%.
 30. A process according to claim 29,wherein the concentration of antioxidant is 0.3-2%.
 31. A processaccording to claim 11, for preparation of a silage aid comprising2,6-di-tert-butyl-4-methylphenol (BHT) and 3-tert-butyl-4-hydroxyanisole(BHA), and formic acid, which comprises a) dissolving BHA in the acid,and b) subsequently, dissolving BHT in the solution obtained in step a).32. A process according to claim 13, for preparation of a silage aidcomprising 2,6-di-tert-butyl-4-methylphenol (BHT) and3-tert-butyl-4-hydroxyanisole (BHA), and formic acid, which comprises a)dissolving BHA in the acid, and b) subsequently, dissolving BHT in thesolution obtained in step a).